From the Super Mario Wiki
In The Super Mario Bros. Super Show! live-action segment "Cher's Poochie", Cher, having an emergency dimple appointment with her plastic surgeon, decided to leave her dog, Poochie, in the care of Mario and Luigi at Mario Brothers Plumbing.
After leaving Poochie with Mario, Cher was escorted out of the apartment by Luigi, who kept asking her for her autograph, which Cher gave him, on a pizza.
Later, Cher returned to Mario Brothers Plumbing to pick-up Poochie, who, unbeknownst to her, had his body switched with Mario due to a malfunction in his Pizza Transformer. Confused as to why "Mario" was pawing at her, Cher went over to "Poochie", who caused her to faint due to him talking to her in Mario's voice.
While Cher laid on the floor, unconscious, Luigi attempted to change Poochie and Mario back to normal and used the Pizza Transformer on them; unfortunately, though Mario gained his body back, Poochie's mind was seemingly transferred into Cher's body, with Cher's mind presumably being put into Poochie's body.